Conventional liner hangers are tied back via a larger extension with a seal bore at the top of the preinstalled liner hanger and a smaller tieback stem with outside diameter seals at the bottom of the upper tieback string. In recent years there has been a challenge with tighter tolerance liners. As the outside diameter of the liner to the inside diameter of the casing gap closes, the room for an extension closes. The result is low extension pressure capability due to thin sleeves and reduced cementing capabilities due to high pressures required to circulate cement through the skinny extension outside diameter to casing inside diameter annulus.
This concept is illustrated in FIG. 1. FIG. 1 illustrates a casing 10 inside of which is a liner 12 that is attached and sealed with a liner hanger 14 and liner top packer 16 respectively. The stem 18 is at the lower end of a tieback sting 20 and typically has a plurality of seals 22 that engage the seal bore 24 inside the extension 28. A clearance 26 is needed to allow cement to pass before the packer 16 is set. With the advent of narrower clearances between the liner 12 and the casing 10 the extensions have been made thinner to preserve clearance 26 so as to not increase the equivalent circulating density with undue cement pressure needed to get the cement through a narrow gap 26 if the initial clearance is already reduced. To offset for the reduced clearance the thickness of the extension 12 is reduced.
This invention turns the conventional tieback connection upside down. The tieback receptacle on the top of the liner hanger is a smaller tube for sealing on the outside diameter with dimensions more or less equivalent to the liner pipe. The tieback shoe that is run on the bottom of the tieback string has dimensions that are more or less similar to the extensions of before. A couple of additional improvements are made. The first improvement is the ability to expand the shoe over the tieback receptacle creating a metal to metal seal and sandwiching steel from the pass through inside diameter all the way to the previous casing (in which the liner hanger is set) outside diameter for improved pressure capacity. The second improvement is making the top of the tieback receptacle have 2 different diameters or 2 steps which allow for improved pressure capacity. The smaller diameter at the top allows for a thicker outer section to carry internal pressure before disengaging the seal. The larger diameter below allows for more collapse capacity on the internal piece.
The following art is generally related to tiebacks and expansion: U.S. Pat. No. 7,195,073 Expandable tieback; U.S. Pat. No. 5,259,459 Subsea wellhead tieback connector; U.S. Pat. No. 5,299,642 Subsea wellhead tieback connector; U.S. Pat. No. 4,293,146 VMP Casing tieback; U.S. Pat. No. 4,519,633 Subsea well casing tieback connector; US2009/0277645 Internal Tieback for Subsea Well; U.S. Pat. No. 7,896,081 Internal tieback for subsea well; US2011/0155382 Internal Tieback for Subsea Well; U.S. Pat. No. 8,127,853 Internal tieback for subsea well; US2003/0145996 Externally actuated subsea wellhead tieback connector; U.S. Pat. No. 6,666,272 Externally actuated subsea wellhead tieback connector; U.S. Pat. No. 5,775,427 Internally latched subsea wellhead tieback connector; U.S. Pat. No. 5,279,369 Tieback receptacle with upward and downward facing funnel sections; U.S. Pat. No. 4,653,589 Mudline casing hanger tieback adaptor with adjustable load ring.
US 2010/0314130 is generally related to tubular expansion with a swage using internal supports to enhance the amount of expansion. US 2010/0314130 A1 by Douglas Durst of Enventure shows mid-string packing elements including a spacer that. US 2010/0089591 A1 by Gordon Thomson shows an under-gage shape hanger in FIG. 19.
Those skilled in the art will better appreciate additional aspects of the invention from a review of the detailed description and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.